Magnetron cavity resonator assembly



Dec. 10, 1963 D. c. BUCK 4 MAGNETRON CAVITY RESONATOR ASSEMBLY Original Filed May 4, 1961 I8 29 I Kr II I 1 A r 7 \3 22 i .2 i E I3 24 E r/ If) 1 2| 35 DANIEL C. BUCK Jul-L1...

ATTORNEY United States Patent (3 ice 3,114,074 MAGNETRON CAVITY RESONATOR ASSEMBLY Daniel C. Buck, Horseheads, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary or the Navy Original application May 4, 1961, Ser. No. 108,372, now Patent No. 3,064,158, dated Nov. 13, 1962. Divided and this application Nov. 17, 1961, Ser. No. 167,9?

3 Claims. (Cl. 315--39.73)

This invention relates to electronic discharge tubes of the magnetron type adapted to generate ultra-high frequency oscillations and in particular is concerned with tuning of 1a magnetron to convert it from a fixed-tuned oscillator to a tunable device.

This application is a division of my application Serial No. 108,872, filed May 4, 1961, for Magnetron Cavity Resonator Assembly which was copending with this application and is now Patent No. 3,064,158 which issued November 13,1962.

The need for tuning a magnetron oscillator may arise in a situation where the oscillating system or the magnetron is predesigned to operate at a definite frequency, and it is therefore useful to be able to adjust the operating frequency or in the case of an oscillator which is oit frequency, it is useful if it can be brought to operate within the frequency band by effecting a small change in the resonating properties of the oscillator.

The present invention relates to the type of tuning device which is mounted exteriorly of one or more of the resonant segments of a multi-cavity magnetron anode and utilizes a diaphragm arranged for suitable adjustment, for example, by manual, electro-mechanical, hydraulic or electronic means to vary the capacitative reactance of the magnetron.

Tuning by use of a diaphragm has been subject to some deficiencies in the past, particularly when a diaphragm is used to adjust the capacitative reactance of magnetrons of large physical dimensions, since it has been customary or necessary to use a large diaphragm tor accommodating it to the iris structure of the magnetron and the large dliaphragrn has been subject to vibration and thermal distortions. Additionally, the large dimensioned magnetrons have required a large tuning cavity to provide eifective tuning; this has presented a problem in cooling for maintaining the tuning structure at proper temperature.

Specifically, the invention is directed to a design or construction of cavity resonator which is formed with or attached to the exterior of a multi-cavity magnetron structure and is not subject to improper operation by internal vibrations or distortions. The invention is predicated on the idea of a cavity resonator of rectangular shape having a length of one-half the wave length at the frequency of operation of the magnetron with which it is used and is substantially of less width and height. Within the rectangular cavity a plurality of fins or plates are arranged to eiiect a periodic loading of the cavity resonator. The fins of the cavity resonator extend from one wall and have side and end edges which are disposed in spaced relation with the other walls; the resonator communicates with a selected one of the magnetron cavities through an opening in the magnetron anode.

This general design of resonator permits it to be constructed of small dimensions and yet be used with large magnetrons. Specifically, a rectangular housing 3" in length by approximately 1% in width by /3" in height has been used effectively on large rnagnetrons whereas a cylindrical type of resonator used with large magnetrons is approximately 7" in diameter.

One object of the present invention is to provide a cavity resonator structure for a magnetron whereby the 3,111,074 Patented Dec. 10, 1963 frequencies generated by the magnetron may be varied or controlled from a'point externally of the magnetron.

Another object of the invention is to provide a rectangular cavity resonator structure which is of sectional or compartmented design providing for its periodic electrical loading of energy from the magnetron.

Still another object of the invention is to provide a cavity resonator structure utilizing a diaphragm for adjusting the volume of the resonator to provide for desired tuning.

The above and other objects and features of the invention will be fully set forth in the following detailed description, taken in conjunction with the accompanying drawings, in which:

.FIG. 1 is a perspective of a magnetron and an external cavity resonator assembly of the present invention with portions of the assembly removed to show details.

FIG. 2 is a sectional view on the line 22 of FIG. 1 looking in the direction of the arrows.

FIG. 3 is a longitudinal section of a modified magnetron and external cavity resonator assembly.

Referring to FIG. 1, one type of cavity resonator of the invention is shown at 10 and assembled with a magnetron indicated at "11 which is of the type having an anode block 12 formed with a plurality of generally cylindrical shaped cavities 13. The anode block 12 is cylindrical and is enclosed within a housing having a cylindrical side wall 14 and similar end walls 1515. At 16 is shown the central cylindrical reaction space of the magnetron which communicates with the cavities 13 through coupling channels or slots 17 and has disposed centrally thereof a cathode .18 which is in the form of a cylindrical rod and supported in position by suitable means, as shown, for example, by Patent No. 2,466,765 to P. L. Hantman. The anode block 12 will preferably be constructed of a conductive material in order that the surfaces of the cavities "13 will be sufficiently conductive to function as reflectors of the electro-magnetic waves of the frequencies which are generated by the magnetron.

The resonator 10 is in the form of a rectangular housing which has substantially greater length than width or height and is secured to the cylindrical wall 14- of the magnetron in sealed relation therewith. As shown in FIG. 1, the upper and lower walls 20 and 21', respectively, of the resonator 10 are in the form of extensions of the annular sidewall 14 of the magnetron; the resonator has a closed outer end 22 and sidewalls 23-23 as in FIG. 2. The inner end wall of the resonator 10 is formed by a portion of the anode 12 and is in communication with a selected cavity identified at 13' through a resonant aperture 24 formed in the end wall portion of anode 12 providing an arrangement for communication between the resonator 10 and the reaction space 16 of the magnetron 1-1. A group of rectangular fins or plates 25 have their upper edges fixed to upper wall 20 of the resonator and extend therefrom in parallel relation with end wall 22 toward the bottom wall 21 providing a space 30 therewith which is defined by the plane of the lower edges of the fins 25. The fins, which extend transversely of the resonator, terminate short of the sidewalls 23-23- and provide other spaces 31 and 32 with the sidewalls and which communicate with the space 30, the spaces 31 and 32 being defined by the planes or" the respective side edges of the fins 25.

The principal electric and magnetic fields of the resonator 10 of the assembly are indicated respectively by the arrows at E and H. The capacitance between the edges of adjacent fins may be adjusted by the provision of a diaphragm 35, disposed as shown in FIG. 1, adjacent the lower wall 21, and having its peripheral edges in tight fitting but movable relation with the side walls and 3 arranged to be adjusted by any suitable means or, the lower wall 21 could be formed of flexible diaphragm material. For adjustment of the diaphragm, a shaft 36 is arranged to adjust the volume of the cavity resonator and as shown is screw-threadedly mounted in the lower wall 21 for manipulation by its knurled end 37.

In FIG. 3, the fins are formed in sets. The fins of one set are indicated at 50 while the fins of the other set are indicated at 51, one set of fins as 50 are secured to the top wall 20 and extend toward the bottom wall 21 while the fins '51 of the other set are secured to a diaphragm 52 which is disposed adjacent the bottom Wall 21. Ad justment is made by means of the adjusting shaft 36 in the manner of FIGS. 1 and 2.

While there has been described what is at present considered to be the preferred embodiments of this invention, it will be obvious that various changes may be made therein without departing from the scope of the invention.

I claim:

l. A tunable magnetron oscillator of the type comprising an annular anode ring having a group ofcircum'ferentially spaced oscillator cavities disposed inwardly of its outer peripheral wall, a slot communicating through the peripheral wall with one of said cavities, a cavity resonator formed of pairs of opposed walls providing a boxlike construction integral with the anode ring and extending outwardly thereof, the inner wall of said resonator being formed of a portion of the anode ring bounding saidslot, a first group of rectangular fins arranged in spaced parallel relation with each other and with the walls of one pair of opposed walls, each of said fins having one edge secured to one wall of a second pair of opposed walls and its other edges spaced from the other wall of said second pair of opposed side walls and from both walls of a third pair of opposed walls, a fiat diaphragm in the resonator adjacent said other wall of the second pair of opposed walls, a second group of rectangular fins having one edge secured to said diaphragm and their other edges spaced from the other walls of said resonator, said second group of fins being parallel with and spaced from said first group of fins and means for adjusting said diaphragm to vary the volume of the resonator.

2. A tunable magnetron oscillator of the type comprising an annular anode ring having a group of circumferentially spaced oscillator cavities disposed inwardly of its outer peripheral wall, a slot communicating through the peripheral wall with one of said cavities, a cavity resonator formed of pairs of opposed wall-s providing a boxlike construction integral with the anode ring and extending outwardly thereof, the inner wall of said resonator being formed of a portion of the anode ring bounding said slot, a first group of rectangular fins arranged in spaced parallel relation with said inner wall of the resonator, each of said fins having one edge secured to one wall of a pair of opposed side walls and its other edges spaced from the other wall of said pair of opposed side walls and from both walls of the other pair of opposed side walls, a fiat diaphragm in the resonator adjacent said other wall of the pair of opposed walls, a second 'group' of said resonator, said second group of fins being parallel with and spaced from said first group of this and means for adjusting said diaphragm to vary the volume of the resonator. J I

3. 1% tunable magnetron oscillator of the type comprising an annular anode ring having a group of circumferentia'lly spaced oscillator cavities disposed inwardly of its outer peripheral wall, a slot communicating through the peripheral wall with one of said cavities, a cavity resonator formed of pairs of opposed Walls providing a boxlike construction integral with the anode ring and extending outwardly thereof, the inner wall of said resonator being formed of a portion of the anode ring bounding said slot, a first group of rectangular fins arranged in spaced parallel relation with said inner wall of the resonator, each of said fins having one edge secured to one wall of a pair of opposed side walls and its other edges spaced from the other wall of said pair of opposedside walls and from both wallsof the other pair of opposed side walls, a flat diaphragm in the resonator adjacent said other wall of the pair of opposed walls, a second group of rectangular fins having 'one edge secured to said diaphragm and their other edges spaced from the other walls of said resonator, said second group of fins being disposed in interdigitating relation with the first group of fins and means for adjusting the diaphragm to vary the volume of the resonator. r

I References Qited in the file of this patent UNITED srarns' PATENTS 

1. A TUNABLE MAGNETRON OSCILLATOR OF THE TYPE COMPRISING AN ANNULAR ANODE RING HAVING A GROUP OF CIRCUMFERENTIALLY SPACED OSCILLATOR CAVITIES DISPOSED INWARDLY OF ITS OUTER PERIPHERAL WALL, A SLOT COMMUNICATING THROUGH THE PERIPHERAL WALL WITH ONE OF SAID CAVITIES, A CAVITY RESONATOR FORMED OF PAIRS OF OPPOSED WALLS PROVIDING A BOXLIKE CONSTRUCTION INTEGRAL WITH THE ANODE RING AND EXTENDING OUTWARDLY THEREOF, THE INNER WALL OF SAID RESONATOR BEING FORMED OF A PORTION OF THE ANODE RING BOUNDING SAID SLOT, A FIRST GROUP OF RECTANGULAR FINS ARRANGED IN SPACED PARALLEL RELATION WITH EACH OTHER AND WITH THE WALLS OF ONE PAIR OF OPPOSED WALLS, EACH OF SAID FINS HAVING ONE EDGE SECURED TO ONE WALL OF A SECOND PAIR OF OPPOSED WALLS AND 